Applicant is aware of U.S. Pat. No. 5,288,102 which issued Feb. 22, 1994 to Machida for a Vehicle Height Control System. Machida discloses a compact vehicle height control system capable of changing the spring constant of gas springs to thereby control the vehicle attitude stabilizing characteristics so as to provide a comfortable vehicle ride. Pilot-controlled directional control valves are interposed in passages that connect first and second gas springs in parallel. When the pilot-controlled directional control valves are opened, the first and second gas springs are communicated with respective cylinders in parallel, whereas, when the directional control valves are closed, only the first gas springs are communicated with the cylinders, thereby changing the spring constant. The pilot-controlled directional control valves are hydraulically operable, thereby eliminating solenoid operated valves.
In the present invention it is an object to provide that which is neither taught nor suggested by Machida, namely a suspension system which employs ride cushion air reservoirs in parallel to provide for a more plush, well cushioned suspension for a coach while driving which is adapted to address the problem with such a soft suspension where a motor coach will, for example, dive during cornering. Thus, it is desirable, and an object of the present invention to make the suspension more firm as the coach enters a corner or otherwise subject to accelerations not ordinarily encountered during straight and level or gentle curves in the road. This is accomplished in the present invention by the use of lock out or “anti-dive” valves which close off the parallel air reservoirs from the suspension air-springs. It is a further object to provide for ride levelling and levelling of the vehicle about three axes.